Lines 5 and 12 are assigned arglist-intro syntax since they are
the first line following the open parenthesis, and lines 7 and 14 are
assigned arglist-close syntax since they contain the parenthesis
that closes the argument list.

Lines that continue argument lists can be assigned one of two syntactic
symbols. For example, Lines 2 and 17
are assigned arglist-cont-nonempty syntax. What this means
is that they continue an argument list, but that the line containing the
parenthesis that opens the list is not empty following the open
parenthesis. Contrast this against lines 6 and 13 which are assigned
arglist-cont syntax. This is because the parenthesis that opens
their argument lists is the last character on that line.

Syntactic elements with arglist-intro,
arglist-cont-nonempty, and arglist-close contain two
buffer positions: the anchor position (the beginning of the
declaration or statement) and the position of the open parenthesis.
The latter position can be used in a line-up function (see Line-Up Functions).

Note that there is no arglist-open syntax. This is because any
parenthesis that opens an argument list, appearing on a separate line,
is assigned the statement-cont syntax instead.